The present invention relates to an air bag cover, and a thermoplastic elastomer composition therefor.
An airbag cover of an airbag system for an automobile is demanded to have stiffness suitable for uses such as an airbag cover for a driver's seat, an airbag cover for a passenger's seat and the like, have high tensile elongation at break to avoid burst of the air bag cover at a portion other than a tear line portion, which is thin-walled portion of an air bag cover provided for bursting an air bag cover at the time of developing an air bag, have high low temperature impact strength to withstand use in cold climates, and have a suitable appearance to interior parts of an automobile.
There are proposed many injection molded air bag covers produced from a polyolefin-based thermoplastic elastomer composition composed of a propylene-based resin and an ethylene-propylene-nonconjugated diene copolymer rubber. For example, in JP-A-8-27331, an injection molded article comprising a thermoplastic elastomer composition composed of a propylene-ethylene random copolymer, an ethylene-propylene-nonconjugated diene copolymer rubber and low-density polyethylene is proposed. Also, in JPA-2000-72937, an injection molded article, which comprises a thermoplastic elastomer composition composed of a propylene-ethylene copolymer, a propylene-1-butene random copolymer and two types of ethylene-propylene-5-ethylidene-2-norbornene copolymer rubbers, is proposed. Moreover, in JP-A-2008-45037, an injection molded article, which comprises a thermoplastic elastomer composition composed of a propylene-based resin produced by multi-stage polymerization and an ethylene-propylene-5-ethylidene-2-norbornene copolymer rubber, is proposed.